HK1237809B - Method of producing nitride fluorescent material, nitride fluorescent material, and light-emitting device using the same - Google Patents

Description

Method for manufacturing nitride phosphor, nitride phosphor and light-emitting device

Technical Field

The present invention relates to a method for manufacturing a nitride phosphor, a nitride phosphor and a light-emitting device.

Background Art

Light-emitting devices, which combine light-emitting diodes (LEDs) and phosphors, are widely used in lighting devices, backlight sources for liquid crystal displays, and the like. For example, when using a light-emitting device in a liquid crystal display, it is preferable to use a phosphor with a narrow half-width (FWHM) to increase the color reproduction range.

Examples of such phosphors include red-emitting SrLiAl ₃ N ₄ :Eu (hereinafter also referred to as "SLAN phosphor"). For example, Patent Document 1 and Non-Patent Document 1 (Philipp Pust et al. "Narrow-band red-emitting Sr[LiAl ₃ N ₄ ]:Eu ²⁺ as a next-generation LED-phosphor material," Nature Materials, NMAT 4012, Vol. 13, September 2014) disclose SLAN phosphors having a narrow half-width (FWHM) of 70 nm or less and a peak emission wavelength near 650 nm.

As disclosed in Non-Patent Document 1, SLAN phosphors can be produced as follows: raw material powders containing lithium aluminum hydride (LiAlH ₄ ), aluminum nitride (AlN), strontium hydride (SrH ₂ ) and europium fluoride (EuF ₃ ) are weighed in a stoichiometric ratio such that Eu reaches 0.4 mol%, mixed, added to a crucible, and fired at 1000°C for 2 hours in an atmosphere of a mixed gas of hydrogen and nitrogen at atmospheric pressure.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application No. 2015-526532

Non-patent literature

Non-Patent Document 1: Philipp Pust et al. “Narrow-band red-emitting Sr[LiAl ₃ N ₄ ]:Eu ²⁺ as a next-generation LED-phosphor material” Nature Materials, NMAT4012, VOL13 September 2014

Summary of the Invention

Problems to be solved by the invention

However, there is room for further improvement in the luminescence intensity of SLAN phosphors. An object of the present invention is to provide a method for producing a nitride phosphor, a nitride phosphor, and a light-emitting device that can produce a nitride phosphor having high luminescence intensity.

Solutions to the Problem

Means for solving the above-mentioned problems are as follows, and the present invention includes the following embodiments.

A first embodiment of the present invention relates to a method for producing a nitride phosphor, wherein the nitride phosphor comprises a fired product having a composition represented by the following formula (I), wherein the content of oxygen is 2% by mass or more and 4% by mass or less.

The production method includes the steps of preparing a fired product having a composition represented by the above formula (I), and mixing the fired product with a polar solvent having a relative dielectric constant of 10 or more and 70 or less at 20°C.

M ^a _v M ^b _w M ^c _x M ^d _y N _z (I)

(In formula (I), ^Ma is at least one element selected from Sr, Ca, Ba, and Mg, ^Mb is at least one element selected from Li, Na, and K, ^Mc is at least one element selected from Eu, Mn, Tb, and Ce, ^Md is at least one element selected from Al, B, Ga, and In, and v, w, x, y, and z are numbers that satisfy 0.8≤v≤1.1, 0.8≤w≤1.1, 0.001<x≤0.1, 2.0≤y≤4.0, and 3.0≤z≤5.0, respectively.)

A second embodiment of the present invention relates to a method for producing a nitride phosphor, comprising the steps of preparing a fired product having a composition represented by the following formula (I), mixing the fired product with a polar solvent,

The polar solvent is an alcohol and/or a ketone containing 0.01% by mass or more and 12% by mass or less of water.

M ^a _v M ^b _w M ^c _x M ^d _y N _z (I)

(In formula (I), ^Ma is at least one element selected from Sr, Ca, Ba, and Mg, ^Mb is at least one element selected from Li, Na, and K, ^Mc is at least one element selected from Eu, Mn, Tb, and Ce, ^Md is at least one element selected from Al, B, Ga, and In, and v, w, x, y, and z are numbers that satisfy 0.8≤v≤1.1, 0.8≤w≤1.1, 0.001<x≤0.1, 2.0≤y≤4.0, and 3.0≤z≤5.0, respectively.)

A third embodiment of the present invention relates to a nitride phosphor including a fired product having a composition represented by the following formula (I), wherein the content of oxygen element is 2% by mass or more and 4% by mass or less.

M ^a _v M ^b _w M ^c _x M ^d _y N _z (I)

(In formula (I), ^Ma is at least one element selected from Sr, Ca, Ba, and Mg, ^Mb is at least one element selected from Li, Na, and K, ^Mc is at least one element selected from Eu, Mn, Tb, and Ce, ^Md is at least one element selected from Al, B, Ga, and In, and v, w, x, y, and z are numbers that satisfy 0.8≤v≤1.1, 0.8≤w≤1.1, 0.001<x≤0.1, 2.0≤y≤4.0, and 3.0≤z≤5.0, respectively.)

A fourth embodiment of the present invention relates to a light-emitting device including a nitride phosphor and an excitation light source.

According to one embodiment of the present invention, a method for manufacturing a nitride phosphor, a nitride phosphor, and a light-emitting device capable of obtaining a nitride phosphor having high luminous intensity can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[Fig. 1] Fig. 1 is a schematic cross-sectional view showing an example of a light-emitting device.

FIG2 shows X-ray diffraction patterns of nitride phosphors according to Examples and Comparative Examples of the present invention, and X-ray diffraction patterns of a compound ( _SLAN ) represented by _Sr3Al2 (OH) ₁₂ , _LiAl2 (OH) _7.2H2O , _{and SrLiAl3N4 .}

[Fig. 3] Fig. 3 shows the emission spectra of the relative emission intensity with respect to the wavelength for the nitride phosphors of the examples and comparative examples of the present invention.

[Figure 4] Figure 4 is an SEM photograph of the nitride phosphor of Example 1.

[Figure 5] Figure 5 is an SEM photograph of the nitride phosphor of Example 4.

[Figure 6] Figure 6 is an SEM photograph of the nitride phosphor of Comparative Example 6.

Explanation of symbols

10: Light-emitting element

50: Sealing component

71: First phosphor

72: Second phosphor

100: Light-emitting device

DETAILED DESCRIPTION

Hereinafter, the manufacturing method of the nitride phosphor of the present application, the nitride phosphor and the light-emitting device will be described in conjunction with the embodiments. It should be noted that the embodiments shown below are examples given to concretize the technical ideas of the present invention, and the present invention is not limited to the following manufacturing method of the nitride phosphor, the nitride phosphor and the light-emitting device. It should be noted that the relationship between the color name and the chromaticity coordinates, the relationship between the wavelength range of light and the color name of monochromatic light, etc., are carried out in accordance with JIS Z8110. In addition, with respect to the content of each component in the composition, when there are multiple substances corresponding to each component in the composition, unless otherwise specified, it represents the total amount of the multiple substances present in the composition.

[Method for producing nitride phosphor]

A method for manufacturing a nitride phosphor according to an embodiment of the present invention is a method for manufacturing a nitride phosphor comprising a fired product having a composition represented by the following formula (I) and an oxygen element content of greater than 2 mass % and less than 4 mass %, wherein the method includes: preparing a fired product having a composition represented by the above formula (I), and mixing the above fired product with a polar solvent having a relative dielectric constant of greater than 10 and less than 70 at 20°C.

M ^a _v M ^b _w M ^c _x M ^d _y N _z (I)

Here, in formula (I), ^Ma is at least one element selected from Sr, Ca, Ba and Mg, ^Mb is at least one element selected from Li, Na and K, ^Mc is at least one element selected from Eu, Mn, Tb and Ce, ^Md is at least one element selected from Al, Si, B, Ga, In, Ge and Sn, particularly preferably at least one element selected from Al, B, Ga and In, and v, w, x, y and z are numbers that satisfy 0.8≤v≤1.1, 0.8≤w≤1.1, 0.001＜x≤0.1, 2.0≤y≤4.0, and 3.0≤z≤5.0, respectively.

In addition, the manufacturing method of the nitride phosphor of an embodiment of the present invention includes: preparing a fired product having a composition represented by the above-mentioned formula (I), and mixing the above-mentioned fired product with a polar solvent, wherein the above-mentioned polar solvent is an alcohol and/or ketone containing more than 0.01 mass% and less than 12 mass% of water.

In the method for producing a nitride phosphor of this embodiment, it is preferred that, in the composition represented by the above formula (I), ^Ma contains at least one of Sr and Ca, ^Mb contains Li, ^Mc is Eu, and Md ^is Al.

The production method of the present embodiment includes a step of mixing the particulate fired product obtained by heat treatment and the polar solvent.

With respect to the phosphor obtained by the manufacturing method of this embodiment, it is believed that by mixing a fired product having a composition represented by formula (I) with the polar solvent, while dispersing the fired product particles, water contained in the polar solvent can be used to form, for example, hydroxides or oxides on the surface or at least a portion near the surface of the fired product particles. Therefore, it is believed that by adjusting, for example, the refractive index near the surface of the phosphor particles, light can be efficiently extracted from the interior of the phosphor particles, resulting in increased luminous intensity of the phosphor.

[Process of preparing the fired product]

The production method of the present embodiment includes preparing a fired product represented by the above formula (I) by heat-treating a raw material mixture obtained by mixing various raw materials to obtain the fired product.

(Raw material mixture)

For the raw material mixture used in the manufacturing method of the present embodiment, as long as a fired product with the composition shown in the above-mentioned formula (I) can be obtained, there is no particular restriction on the material contained in its raw material mixture. For example, the raw material mixture may include at least one raw material selected from the simple substance of the metal element constituting the composition shown in the above-mentioned formula (I) and their metal compounds. As such metal compounds, hydrides, nitrides, fluorides, oxides, carbonates, chlorides, etc. can be listed. With regard to raw materials, from the viewpoint of improving luminescent properties, it is preferably at least one selected from hydrides, nitrides and fluorides. In the case of oxides, carbonates, chlorides, etc. as metal compounds included in the raw material mixture, their content is preferably 5% by mass or less, more preferably 1% by mass or less in the raw material mixture. In the metal compound, for fluorides or chlorides, compounds whose element ratio of cations reaches the target composition can also be made and added to the raw material mixture, which also has the effect of being a flux component described later.

The raw material mixture preferably contains the following metal compounds: a metal compound containing a metal element selected from Sr, Ca, ^Ba and Mg as ^Ma , a metal compound containing a metal element selected from Li, Na and K as ^Mb , a metal compound containing a metal element selected from Eu, Mn, Tb and Ce as Mc, and a metal compound containing a metal element selected from Al, Si, B, Ga, In, Ge and Sn as ^Md .

Specific examples of the metal compound containing a metal element ( ^Ma element) selected from Sr, Ca, Ba, and Mg (hereinafter also referred to as "first metal compound") include _SrN2 , SrN _{, Sr3N2} , _SrH2 , _SrF2 , _Ca3N2 , _CaH2 , _CaF2 , _Ba3N2 , _BaH2 , _BaF2 , _{Mg3N2 , MgH2} , _{and MgF2} , _and at least one selected from these is preferred.

The first metal compound preferably contains at least one of Sr and Ca. When the first metal compound contains Sr, a portion of Sr may be substituted with Ca, Mg, Ba, or the like. Furthermore, when the first metal compound contains Ca, a portion of Ca may be substituted with Sr, Mg, Ba, or the like. This allows the peak emission wavelength of the nitride phosphor to be adjusted.

The first metal compound may be used alone or as a compound such as an imide compound or an amide compound. The first metal compound may be used alone or in combination of two or more.

The metal compound containing a metal element (M ^b element) selected from Li, Na, and K (hereinafter also referred to as the "second metal compound") preferably contains at least Li, and more preferably is at least one of a nitride and a hydride of Li. When the second metal compound contains Li, a portion of the Li may be optionally replaced with Na, K, or the like, and may further contain other metal elements that constitute the nitride phosphor.

Specifically, the second metal compound containing Li is preferably at least one selected from the group consisting of Li ₃ N, LiN ₃ , LiH, and LiAlH ₄ .

The metal compound containing a metal element ( ^Md element) selected from Al, Si, B, Ga, In, Ge, and Sn (hereinafter also referred to as the "third metal compound") may be a metal compound containing substantially only a metal element selected from Al, Si, B, Ga, In, Ge, and Sn as its metal element, or a metal compound in which a portion of the metal element is replaced by another metal element. The third metal compound is preferably a metal compound containing only Al, or a metal compound in which a portion of Al is replaced by another metal element selected from Ga and In of Group 13, and V, Cr, and Co of Period 4, or a metal compound containing, in addition to Al, other metal elements constituting the nitride phosphor, such as Li.

Specific examples of the third metal compound include metal compounds containing Al, such as AlN, AlH ₃ , AlF ₃ , and LiAlH ₄ . It is preferably at least one selected from these.

The third metal compound may be used alone or in combination of two or more.

The metal compound containing a metal element (M ^c element) selected from Eu, Mn, Tb and Ce (hereinafter also referred to as the "fourth metal compound") can be a metal compound that essentially only contains a metal element selected from Eu, Mn, Tb and Ce as its metal element, or it can be a metal compound in which a part of the metal element is replaced by other metal elements.

The fourth metal compound is preferably a metal compound containing Eu, and may also contain Eu as an activator, but a portion of Eu is replaced by Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. It can be considered that by replacing a portion of Eu with other elements, the other elements can act as co-activators, for example. By using a co-activator, the luminescence characteristics of the nitride phosphor can be adjusted. In the case where a mixture that requires Eu is used as a nitride phosphor, the mixing ratio can be changed as needed. Europium mainly has divalent and trivalent energy levels, and the nitride phosphor of this embodiment uses at least Eu ²⁺ as an activator.

Specific examples of the fourth metal compound include _Eu2O3 , EuN, and _EuF3 , preferably at least one selected from _these . The nitride phosphor of this embodiment contains divalent Eu as the luminescent center, but divalent Eu is easily oxidized. Therefore, a metal compound containing trivalent Eu can be used to form the raw material mixture.

In addition to the aforementioned metal elements and metal compounds, the raw material mixture may also contain other metal elements as needed. Other metal elements are generally present in the raw material mixture in the form of oxides, hydroxides, etc., but are not limited to these. Other metal elements may also be in the form of metal elements, nitrides, imides, amides, other inorganic salts, etc., and may also be pre-included in the aforementioned raw material mixture.

The raw material mixture may also include a flux. By including a flux in the raw material mixture, the reaction between the raw materials is further promoted, and the solid phase reaction can be carried out more uniformly, thereby obtaining a phosphor with a large particle size and better luminescent properties. It can be considered that this is because, for example, when the heat treatment in the manufacturing method is carried out at a temperature of more than 1000°C and less than 1300°C, when a halide or the like is used as a flux, the temperature is substantially the same as the generation temperature of the liquid phase of the halide. As a halide used as a flux, chlorides and fluorides of rare earth metals, alkaline earth metals, and alkali metals can be used. As a flux, it can be added to the raw material mixture in the form of a compound whose element ratio of cations reaches the target composition, or it can be added in the form of an addition after further adding each raw material to the target composition. Fluorides are particularly preferred.

When the raw material mixture contains a flux, the flux component promotes reactivity. However, if the flux component is excessive, there is a risk of reduced workability during the production process of the nitride phosphor or a decrease in the luminescence intensity of the resulting nitride phosphor. Therefore, the flux content in the raw material mixture is preferably 10% by mass or less, and more preferably 5% by mass or less. The raw material mixture may contain fluorides such as _SrF2 and _EuF3 . When such fluorides are used, the fluorine content in the final phosphor is preferably 0.1% by mass or more and 1% by mass or less.

(Heat Treatment)

The production method of this embodiment includes heat-treating the raw material mixture in a nitrogen atmosphere to prepare a fired product having a composition represented by the above formula (I).

The fired product having the composition represented by the above formula (I) can be prepared by heat-treating a mixture of raw materials in a nitrogen-containing gas atmosphere at a temperature of 1000° C. to 1400° C. and a pressure of 0.2 MPa to 200 MPa.

By heat-treating the raw material mixture at a predetermined temperature in a pressurized atmosphere containing nitrogen, a fired product having a desired composition and high luminescence intensity can be efficiently produced. The fired product particles can also be used as phosphor particles.

The raw material mixture prepared in a manner to achieve the composition represented by the above formula (I) is heat-treated to obtain a fired product. The heat treatment can be performed using, for example, a gas pressurized electric furnace. As for the heat treatment temperature, it can be carried out in a range of 1000°C to 1400°C, preferably 1000°C to 1300°C, more preferably 1100°C to 1300°C. When the heat treatment temperature is above 1000°C, a fired product having the target composition ratio can be formed. In addition, when the temperature is below 1400°C, decomposition of the fired product will not occur, and there is no hidden danger of destroying the luminescent properties of the nitride phosphor obtained from the fired product.

Alternatively, the heat treatment may be performed in two steps (multi-step firing) by performing a first step heat treatment at 800°C to 1000°C, then gradually increasing the temperature to perform a second step heat treatment at 1000°C to 1400°C. Crucibles, boats, and the like made of carbon materials such as graphite, boron nitride (BN), alumina ( _Al2O3 ), W, or Mo can be used for heat treatment of _the raw material mixture.

The heat treatment gas atmosphere is preferably a gas atmosphere containing nitrogen. The gas atmosphere containing nitrogen may be a gas atmosphere containing at least one selected from the group consisting of hydrogen, argon, carbon dioxide, carbon monoxide, ammonia, etc. in addition to nitrogen. The ratio of nitrogen in the heat treatment gas atmosphere is preferably 70% by volume or more, more preferably 80% by volume or more.

The heat treatment is preferably carried out in a pressurized gas atmosphere of 0.2 MPa to 200 MPa. The target nitride phosphor decomposes more easily at higher temperatures, but by forming a pressurized gas atmosphere, decomposition can be suppressed, and higher luminescence intensity can be achieved. The pressurized gas atmosphere is preferably 0.2 MPa to 1.0 MPa, more preferably 0.8 MPa to 1.0 MPa, in terms of gauge pressure. By increasing the pressure of the atmosphere during the heat treatment, the decomposition of the phosphor compound during the heat treatment can be suppressed, thereby obtaining a phosphor with high luminescence characteristics.

The heat treatment time may be appropriately selected depending on the heat treatment temperature, gas pressure, etc. The heat treatment time is, for example, 0.5 hours to 20 hours, preferably 1 hour to 10 hours.

Next, as an example of the manufacturing method of this embodiment, a manufacturing method for a fired product having a designed composition of Sr _0.993 Eu _0.007 LiAl ₃ N _4, which can obtain a nitride phosphor including a fired product having a composition represented by the above formula (I), is specifically described. However, the manufacturing method of the nitride phosphor is not limited to the following manufacturing method.

As the metal compounds constituting the raw material mixture, powders of _SrNu (equivalent to a mixture of _SrN2 and SrN with u = 2/3), _LiAlH4 , AlN, and _EuF3 were weighed in an inert gas glove box to achieve a ratio of Sr:Eu:Li:Al = 0.9925:0.0075:1.2:3. These powders were mixed to obtain a raw material mixture. Because Li tends to scatter during firing, a slightly higher ratio than the theoretical composition ratio was added. It should be noted that this embodiment is not limited to this composition ratio.

By heat treating the raw material mixture in a nitrogen atmosphere, a granular fired product represented by Sr _0.993 Eu _0.007 LiAl ₃ N ₄ can be obtained. However, the ratio of each element in the composition formula is a theoretical composition ratio estimated based on the mixing ratio of the raw material mixture. The coefficients of each element are removed from the composition formula. Elements such as F, which are partially scattered during firing, are also removed from the composition formula. As mentioned above, the actual composition contains a certain amount of oxygen. In addition, by using fluorides that also act as flux components, a certain amount of fluorine will be included in the fired product. The ratio of Sr, Eu, and Li in the composition formula is a value calculated based on the ratio of each element contained in the composition with the Al composition ratio of 3 as a benchmark. Since decomposition and scattering may occur during heat treatment, the ratio of Sr, Eu, and Li as the charging ratio may sometimes be different from the theoretical composition ratio. In addition, by changing the mixing ratio of each raw material, a nitride phosphor with a target composition can be obtained.

In addition, other manufacturing methods other than those described above may be used. A fired product having the target composition represented by the above formula (I) can be produced by weighing the metal elements so as to achieve a predetermined composition ratio, melting them to form an alloy, pulverizing the alloy, and sintering the pulverized alloy in a nitrogen atmosphere using a gas pressure sintering furnace or a HIP furnace using a hot isostatic pressing (HIP) method.

[Mixing process of fired product and polar solvent]

The production method of the present embodiment includes a step of mixing a fired product having a composition represented by the above formula (I) and a polar solvent.

The manufacture method of present embodiment is by the operation that the burnt material with the composition shown in above-mentioned formula (I) and polar solvent are mixed and the particle dispersion of burnt material is made.Can think that, in this process, at least a portion of burnt material particle surface can be subject to the influence of polar solvent and form such as hydroxide, oxide on the particle surface of burnt material.Can think that the fluor that obtains like this has the compound different from the composition of fluor at least a portion of surface, thus, by adjusting such as refractive index near the surface of fluor particle, can efficiently derive light, and its result, can improve the luminous intensity of fluor.

In addition, the manufacturing method of this embodiment includes a step of mixing particles of a fired product having the composition shown in the above formula (I) with a polar solvent, which can take into account both the dispersion of the particles of the fired product and the adjustment of the refractive index of the surface of the fired product particles, thereby efficiently manufacturing a nitride phosphor with high luminous intensity.

(Polar solvent)

In the production method according to the embodiment of the present invention, the polar solvent is a polar solvent having a relative dielectric constant of 10 to 70 at 20° C., or an alcohol and/or ketone containing 0.01 to 12 mass % of water.

The relative dielectric constant of the polar solvent at 20°C is more preferably 10 or greater, and even more preferably 15 or greater. The relative dielectric constant of the polar solvent at 20°C is preferably 35 or less.

Even when the polar solvent is an alcohol and/or ketone containing 0.01% by mass or more and 12% by mass or less of water, it is preferred that the relative dielectric constant at 20° C. be 10 or more and 35 or less.

Polar solvents with a relative dielectric constant of less than 10 at 20°C are not preferred because their affinity for water is low, making it difficult for the surface of the phosphor particles to react with water, leading to reduced dispersibility of the fired product. Polar solvents with a relative dielectric constant of more than 70 at 20°C are not preferred because their affinity for water is too high, and there is a tendency for the fired product (phosphor) to decompose due to the reaction with water.

Examples of polar solvents having a relative dielectric constant of 10 to 70 at 20°C include ethyl acetate, tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, alcohols having a linear or branched alkyl group having 1 to 8 carbon atoms, carboxylic acids such as formic acid and acetic acid, and ketones such as acetone. Polar solvents having a relative dielectric constant of 10 to 70 at 20°C are preferably alcohols and/or ketones.

When using alcohols and/or ketones as polar solvents, lower alcohols and/or ketones having a linear or branched alkyl group with 1 to 4 carbon atoms are preferred. More preferably, the polar solvent is at least one selected from methanol (relative dielectric constant 33), ethanol (relative dielectric constant 24), 1-propanol (relative dielectric constant 20), 2-propanol (relative dielectric constant 18), and acetone (relative dielectric constant 21). The polar solvent may be a single polar solvent or a combination of two or more polar solvents.

In the manufacturing method of the present embodiment, the polar solvent may also contain water having a relative dielectric constant of 80 at 20°C, and the content of water in the polar solvent as alcohol and/or ketone is 0.01 mass % or more and 12 mass % or less. In addition, the content of water in the polar solvent having a relative dielectric constant of 10 or more and 70 or less at 20°C is preferably 0.01 mass % or more and 12 mass % or less. The content of water in the polar solvent is more preferably 0.1 mass % or more and 10 mass % or less. In general, water is often used when dispersing phosphor particles. The nitride phosphor containing a fired product having the composition described in the above formula (I) has a tendency to react with water and decompose in the presence of more than a certain amount of water. In the manufacturing method of the present embodiment, by containing a certain amount of water in the polar solvent, a compound having a composition different from that of the nitride phosphor can be formed on at least a portion of the particle surface of the fired product while suppressing the decomposition of the fired product constituting the phosphor particles. It is considered that this adjusts, for example, the refractive index near the surface of the phosphor particles, and effectively extracts light to the outside of the phosphor particles, thereby increasing the emission intensity of the phosphor.

In the manufacturing method of this embodiment, the particles of the fired product are preferably stirred in a polar solvent. By stirring the fired product in a polar solvent, the particles of the fired product can be dispersed. When the fired product is stirred in a polar solvent, the dispersion of the particles of the fired product is promoted, so a dispersion medium such as alumina balls or zirconia balls can also be added. It is believed that by stirring the fired product in a polar solvent, the particles of the fired product can be dispersed and hydroxides and oxides can be formed on at least a portion of the surface of the particles. Polar solvents can improve the luminescent properties of nitride phosphors, while in contrast, it is difficult to achieve improvement in the luminescent properties in non-polar solvents. It is believed that this is because when water is contained in a polar solvent, hydroxides and oxides can be formed on at least a portion of the surface of the phosphor particles, while in contrast, non-polar solvents have low affinity with water, so it is difficult for water to form hydroxides and oxides on the surface of the phosphor particles.

[Grading process]

The manufacturing method of the present embodiment may also include a step of classifying the nitride phosphor to obtain a nitride phosphor with an average particle size of 4.0 μm or more after the step of mixing the fired product and the polar solvent. Through the classification step, the average particle size of the nitride phosphor can be made to reach a given value or more, so that a nitride phosphor with an excitation light absorption rate and luminous intensity further improved relative to the nitride phosphor can be obtained. Specifically, the classification step obtains a nitride phosphor with an average particle size of 4.0 μm or more by adopting sieving, gravity-based sedimentation classification in the solution, centrifugal separation, etc. According to the manufacturing method of the present embodiment, it is preferred to obtain a nitride phosphor with an average particle size of 4.0 to 20 μm through the classification step, and it is more preferred to obtain a nitride phosphor with an average particle size of 5.0 to 18 μm.

A specific example of the nitride phosphor obtained by the manufacturing method of this embodiment will be described later, but the nitride phosphor obtained by the manufacturing method of this embodiment has a composition represented by formula (I). In addition, with respect to the nitride phosphor obtained by the manufacturing method of this embodiment, the content of oxygen element in the nitride phosphor is greater than 2% by mass and less than 4% by mass.

The oxygen contained in nitride phosphors may include not only the oxygen contained in the hydroxides and oxides believed to be formed by mixing the fired product with a polar solvent, but also the oxygen contained in the hydroxides and oxides formed on the surface of the phosphor particles when the phosphor particles are exposed to the atmosphere. It is estimated that the hydroxides and oxides formed by exposure to the atmosphere are extremely small.

The nitride phosphor obtained by the production method of this embodiment has a composition represented by the above formula (I), and may further contain fluorine. It is believed that the fluorine contained in the nitride phosphor is derived from the raw material mixture and the aforementioned flux.

(Nitride phosphor)

The nitride phosphor according to the embodiment of the present invention includes a fired product having a composition represented by the following formula (I), and the content of oxygen element is 2 mass % or more and 4 mass % or less.

M ^a _v M ^b _w M ^c _x M ^d _y N _z (I)

Here, in formula (I), ^Ma is at least one element selected from Sr, Ca, Ba and Mg, ^Mb is at least one element selected from Li, Na and K, ^Mc is at least one element selected from Eu, Mn, Tb and Ce, ^Md is at least one element selected from Al, Si, B, Ga, In, Ge and Sn, particularly preferably at least one element selected from Al, B, Ga and In, and v, w, x, y and z are numbers that satisfy 0.8≤v≤1.1, 0.8≤w≤1.1, 0.001＜x≤0.1, 2.0≤y≤4.0, and 3.0≤z≤5.0, respectively.

It should be noted that the nitride phosphor of the present embodiment contains oxygen elements, although not recorded in the composition shown in the above formula (I). The oxygen elements contained in the nitride phosphor of the present embodiment are believed to be mainly derived from the oxygen elements of hydroxides and oxides formed on at least a portion of the surface when the particles of the fired product are mixed with a polar solvent. The oxygen elements contained in the nitride phosphor of the present embodiment may also include oxygen elements from hydroxides and oxides formed on the surface of the particles due to the phosphor particles being placed in the atmosphere. The hydroxides and oxides generated by placing the phosphor particles in the atmosphere are extremely small. The oxygen elements not reflected in the phosphor of the composition shown in the above formula (I) sometimes come from the following supply sources. Sometimes it contains oxygen elements from the following: (1) trace amounts of hydroxides and oxides contained in various nitrides, hydrides, metals, etc. that become the raw material mixture, (2) oxides generated by oxidation of the raw material mixture during heat treatment, and (3) oxygen elements attached to the generated nitride phosphor. However, the content of oxygen element derived from the oxides or attachments of (1) to (3) above is extremely small. The content of oxygen element derived from the oxides or attachments of (1) to (3) above contained in the nitride phosphor of this embodiment is an extremely small amount of less than 0.1% by mass.

Generally speaking, when oxygen is present in a nitride phosphor, the crystal structure of the phosphor can be changed by controlling the molar ratio of oxygen, so that the peak wavelength of the emission of the phosphor is shifted. On the other hand, from the viewpoint of high luminous intensity, a nitride phosphor containing less oxygen is preferred. It can be considered that when the amount of oxygen contained in the nitride phosphor increases, its influence not only stays on the surface of the phosphor particles, but also reaches the interior, causing the crystal structure of the nitride phosphor to become unstable. When the crystal structure of the nitride phosphor becomes unstable, there is a tendency to cause a decrease in the luminous intensity. Therefore, when the nitride phosphor contains oxygen, it is preferred that the oxygen element is contained near the surface of the nitride phosphor.

The oxygen content in the nitride phosphor of this embodiment is 2% to 4% by mass. The oxygen content in the nitride phosphor is preferably 2.2% to 3.8% by mass, and more preferably 2.5% to 3.5% by mass.

When the oxygen content in a nitride phosphor exceeds 4% by mass, the oxygen content increases, and oxygen not only remains on the surface of the phosphor particles but also penetrates into the interior, tending to reduce luminescence intensity. On the other hand, when the oxygen content in a nitride phosphor is less than 2% by mass, it becomes difficult to form hydroxides and oxides near the surface of the phosphor particles that are sufficient to increase light extraction to the outside of the phosphor particles, and thus it tends to be difficult to increase luminescence intensity.

In addition, the nitride phosphor of this embodiment may further contain elemental fluorine, and the content of elemental fluorine is preferably 0.1% by mass or more and 1% by mass or less. The content of elemental fluorine contained in the nitride phosphor is more preferably 0.2% by mass or more and 0.8% by mass or less, and even more preferably 0.3% by mass or more and 0.7% by mass or less. It is speculated that the elemental fluorine contained in the nitride phosphor is derived from the raw material mixture and the aforementioned flux.

When the fluorine content in the nitride phosphor is greater than 0.1 mass % and less than 1 mass %, part of the nitride phosphor decomposes, thereby reducing the possibility of other compounds existing in the nitride phosphor, thereby suppressing the reduction in luminescence intensity caused by the presence of other compounds.

The nitride phosphor of this embodiment preferably has an internal quantum efficiency of 80% or more, and more preferably has an internal quantum efficiency of 81% or more, thereby increasing the emission intensity of the nitride phosphor.

The nitride phosphor of this embodiment preferably has an external quantum efficiency exceeding 55%, and more preferably an external quantum efficiency of 56% or more. This can improve the emission intensity of the nitride phosphor.

In formula (I), from the viewpoint of improving luminescence intensity, it is preferred that ^Ma contains at least one of Ca and Sr. When ^Ma contains at least one of Ca and Sr, the total molar ratio of Ca and Sr contained in ^Ma is, for example, 85 mol% or more, preferably 90 mol% or more.

In addition, from the viewpoint of crystal structure stability, in formula (I), ^Mb preferably contains at least Li. When ^Mb contains Li, the molar ratio of Li contained in ^Mb is, for example, 80 mol% or more, preferably 90 mol% or more.

In formula (I), ^Mc is preferably Eu and ^Md is Al. When ^Mc is Eu and ^Md is Al in formula (I), a nitride phosphor having a narrow half-maximum width of the emission spectrum and a desired wavelength range can be obtained.

As long as v, w, x, y and z in formula (I) satisfy the above numerical ranges, there are no special restrictions. From the viewpoint of crystal structure stability, the values of v and w are respectively greater than 0.8 and less than 1.1, preferably greater than 0.9 and less than 1.05. x is the Eu activation amount, which is appropriately selected so that the desired characteristics can be achieved. x is a number that satisfies 0.001＜x≤0.1, preferably 0.001＜x≤0.02, and more preferably 0.002≤x≤0.015. From the viewpoint of crystal structure stability, y is a number that satisfies 2.0≤y≤4.0, preferably 2.0≤y≤3.5. In addition, also from the viewpoint of crystal structure stability, z is a number that satisfies 3.0≤z≤5.0, preferably 3.0≤z≤4.0.

The nitride phosphor of this embodiment may contain impurities not reflected in the composition of formula (I). Impurities that may be present in the nitride phosphor may be selected from Sc, Y, Ti, Zr, V, Nb, Cr, Mo, Mn, Fe, Ru, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Hf, Ta, W, Re, Os, Ir, Pt, Tl, Pb, and Bi.

The nitride phosphor of this embodiment absorbs light in the short-wavelength region from ultraviolet to visible light, i.e., in the wavelength range of 400 nm to 570 nm, and emits fluorescence with a luminescence peak wavelength in the wavelength range of 630 nm to 670 nm. By using an excitation light source in this wavelength range, a phosphor with high luminescence intensity can be provided. The excitation light source preferably uses an excitation light source having a main luminescence peak wavelength of 420 nm to 500 nm, and more preferably uses an excitation light source having a main luminescence peak wavelength of 420 nm to 460 nm.

The luminescence spectrum of the nitride phosphor has a peak wavelength in the range of 630 nm to 670 nm, preferably 640 nm to 660 nm. Furthermore, the half-width of the luminescence spectrum is, for example, 65 nm or less, preferably 60 nm or less. The lower limit of the half-width is, for example, 45 nm or more.

Nitride phosphors use ^Mc as the luminescence center. When ^Mc is europium (Eu), a rare earth element, the europium (Eu) serves as the luminescence center. However, the luminescence center in this embodiment is not limited to europium; the europium portion of the luminescence center can also be replaced with other rare earth metals or alkaline earth metals. These other elements can be used with europium as co-activators. Stable luminescence is achieved in the divalent rare earth ion Eu2 ⁺ by selecting an appropriate parent crystal.

The average particle size of the nitride phosphor is, for example, 4.0 μm or more, preferably 4.5 μm or more, more preferably 5.0 μm or more, and the average particle size is, for example, 20 μm or less, preferably 18 μm or less.

By setting the average particle size above a predetermined value, the nitride phosphor tends to have a higher excitation light absorption rate and luminescence intensity. Thus, by incorporating a nitride phosphor with excellent luminescence properties into a light-emitting device, as described later, the luminous efficiency of the light-emitting device can be improved. Furthermore, by setting the average particle size below a predetermined value, workability in the light-emitting device manufacturing process can be improved.

Furthermore, the nitride phosphor preferably contains phosphor particles having the aforementioned average particle size at a high frequency. In other words, the nitride phosphor preferably has a narrow particle size distribution. By using nitride phosphor particles with minimal particle size variation, color spots can be suppressed, resulting in a light-emitting device with a good color tone.

In this specification, the average particle size of the nitride phosphor and the average particle size of other phosphors is a volume average particle size, which is a particle size (median diameter) that can be measured using a laser diffraction particle size distribution analyzer (MASTER SIZER 2000 manufactured by Malvern).

It is preferred that most particles of the nitride phosphor have a crystalline structure. For example, since the glass (amorphous) has a loose crystalline structure, the ratio of components in the phosphor is not fixed, and there is a risk of uneven chromaticity. Therefore, in order to avoid this situation, the reaction conditions in the production process must be strictly managed for consistency. Most phosphors with a crystalline structure are easy to manufacture and process. In addition, the phosphor is easy to disperse evenly in the resin, so it is easy to form a sealing component described later. The content of the crystalline structure in the phosphor particles represents the proportion of the luminescent crystalline phase. The nitride phosphor preferably has a crystalline phase of at least 50% by mass, more preferably 80% by mass or more. When the crystalline phase has 50% by mass or more of luminescent properties, practical luminescence can be obtained.

(Light-emitting device)

Next, a light-emitting device using a nitride phosphor as a wavelength conversion member is described. The light-emitting device according to an embodiment of the present invention includes the above-mentioned nitride phosphor and an excitation light source. The excitation light source preferably emits light in the range of 400 nm to 570 nm.

A light-emitting element can be used as an excitation light source. The light-emitting element emits light in a wavelength range of 400 nm to 570 nm. The peak emission wavelength of the light-emitting element is preferably in a wavelength range of 420 nm to 460 nm. By using a light-emitting element with a peak emission wavelength in this range as an excitation light source, a light-emitting device can be constructed that emits mixed light of light from the light-emitting element and fluorescence from the phosphor. Because a portion of the light emitted from the light-emitting element can be effectively used as light for the light-emitting device, a light-emitting device with high luminous efficiency can be obtained.

As the light-emitting element, a semiconductor light-emitting element that emits blue or green light, such as one utilizing a nitride-based semiconductor ( _{InXAlYGa1 -XYN ,} 0≤X, 0≤Y, X+Y≤1), is preferably used. Using a semiconductor light-emitting element as a light source can produce a stable light-emitting device with high efficiency, high linearity of output relative to input, and strong resistance to mechanical shock. The half-value width of the emission spectrum of the light-emitting element can be, for example, 30 nm or less.

The first phosphor included in the light-emitting device includes the nitride phosphor. The nitride phosphor has a composition represented by formula (I), is excited by light with a wavelength range of 400 nm to 570 nm, and has a peak emission wavelength within a range of 630 nm to 670 nm.

For example, the first phosphor can be contained in a sealing resin covering an excitation light source to form a light-emitting device. In a light-emitting device in which the excitation light source is covered by the sealing resin containing the first phosphor, a portion of the light emitted from the excitation light source is absorbed by the first phosphor and emitted as red light. By using an excitation light source that emits light in the wavelength range of 400 nm to 570 nm, the emitted light can be more efficiently utilized. This reduces light loss from the light-emitting device, providing a light-emitting device with high luminous efficiency.

The content of the first phosphor contained in the light-emitting device can be, for example, 1 to 50 parts by mass, and preferably 2 to 30 parts by mass, relative to 100 parts by mass of the sealing resin.

The light-emitting device may also include a second phosphor having a different emission peak wavelength range from that of the first phosphor. For example, by appropriately including a light-emitting element that emits blue light and first and second phosphors excited by the light-emitting element, the light-emitting device can have a wide color reproduction range or high color rendering.

The second phosphor preferably includes, for example, at least one phosphor having a composition represented by any one of the following formulas (IIa), (IIb), (IIc), (IId), (IIe), (IIf), (IIg), (IIh), and (IIi). For example, in order to achieve a wide color reproduction range, the second phosphor more preferably includes at least one phosphor having a composition represented by formula (IIc), (IIe), (IIh), or (IIi).

(Y,Gd,Tb,Lu) ₃ (Al,Ga) ₅ O ₁₂ :Ce (IIa)

(Ba,Sr,Ca) ₂ SiO ₄ :Eu (IIb)

Si _6-p Al _p O _p N _8-p :Eu(0＜p≤4.2) (IIc)

(Ca,Sr) ₈ MgSi ₄ O ₁₆ (Cl,F,Br) ₂ :Eu (IId)

(Ba,Sr,Ca)Ga ₂ S ₄ :Eu (IIe)

(Ba,Sr,Ca) ₂ Si ₅ N ₈ :Eu (IIf)

(Sr,Ca)AlSiN ₃ :Eu (IIg)

K ₂ (Si,Ge,Ti)F ₆ :Mn (IIh)

(Ba,Sr)MgAl ₁₀ O ₁₇ :Mn (IIi)

The average particle size of the second phosphor is preferably 2 μm to 35 μm, more preferably 5 μm to 30 μm. By setting the average particle size to a predetermined value or less, workability in the manufacturing process of the light-emitting device can be improved.

The content of the second phosphor can be appropriately selected depending on the purpose, etc. For example, the content of the second phosphor can be 1 to 200 parts by mass, preferably 2 to 180 parts by mass, based on 100 parts by mass of the sealing resin.

The content ratio of the first phosphor to the second phosphor, for example, the content ratio of the first phosphor to the second phosphor (first phosphor/second phosphor) can be 0.01 to 5, preferably 0.05 to 3, on a mass basis.

The first phosphor and the second phosphor (hereinafter referred to collectively as "phosphors") preferably form a sealing member that covers the light-emitting element together with a sealing resin. Examples of the sealing resin that constitutes the sealing member include epoxy resin and silicone resin.

The total content of the phosphor in the sealing member may be, for example, 5 to 300 parts by mass, preferably 10 to 250 parts by mass, more preferably 15 to 230 parts by mass, and even more preferably 15 to 200 parts by mass, relative to 100 parts by mass of the sealing resin.

The sealing member may further include fillers, light-diffusing materials, and the like in addition to the sealing resin and the phosphor. Examples of fillers and light-diffusing materials include silicon dioxide, titanium oxide, zinc oxide, zirconium oxide, and aluminum oxide. When the sealing member includes a filler, the content thereof can be appropriately selected depending on the intended purpose. For example, the filler content may be 1 to 20 parts by mass relative to 100 parts by mass of the sealing resin.

An example of a light emitting device according to this embodiment will be described with reference to the accompanying drawings. Fig. 1 is a schematic cross-sectional view showing an example of a light emitting device according to this embodiment.

The light-emitting device 100 includes a component 40 having a recess, a light-emitting element 10, and a sealing member 50 that covers the light-emitting element 10. The light-emitting element 10 is arranged in the recess formed by the component 40 and is electrically connected to a pair of positive and negative lead electrodes 20 and 30 arranged in the component 40 via a conductive cable 60. The sealing member 50 is formed by filling the recess with a sealing resin containing a phosphor 70, thereby covering the light-emitting element 10. The sealing member 50 includes, for example, a phosphor 70 that converts the wavelength of light from the sealing resin and the light-emitting element 10. Furthermore, the phosphor 70 includes a first phosphor 71 and a second phosphor 72. Parts of the pair of positive and negative lead electrodes 20 and 30 are exposed outside the component 40. The light-emitting device 100 receives power from the outside through these lead electrodes 20 and 30 and emits light.

The sealing member 50 not only serves as a wavelength conversion member, but also serves as a member for protecting the light-emitting element 10, the first phosphor 71, and the second phosphor 72 from the external environment. In Figure 1, the first phosphor 71 and the second phosphor 72 are unevenly distributed in the sealing member 50. By arranging the first phosphor 71 and the first phosphor 72 close to the light-emitting element 10 in this way, the wavelength of light from the light-emitting element 10 can be effectively converted, thereby obtaining a light-emitting device with excellent luminous efficiency. It should be noted that the configuration of the sealing member 50 including the first phosphor 71 and the first phosphor 72 and the light-emitting element 10 is not limited to being arranged close to them. Considering the influence of heat on the first phosphor 71 and the first phosphor 72, the light-emitting element 10 can also be arranged with a gap between the first phosphor 71 and the first phosphor 72 in the sealing member 50. In addition, by mixing the first phosphor 71 and the first phosphor 72 in a substantially uniform ratio throughout the sealing member 50, light with further suppressed color spots can be obtained.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Production Example 1)

To obtain a nitride phosphor containing a fired product having the composition shown _{in MavMbwMcxMdyNz} ^{, SrNu} (equivalent to _a mixture of ^SrN2 and _SrN with ^u = 2/3 ₎ , _SrF2 , _LiAlH4 , _AlN , and _EuF3 were used as raw materials, with ^Ma being Sr, ^Mb being Li, ^Mc being Eu, and ^Md being Al _. These raw materials were weighed and mixed in an inert gas glove box to achieve a molar ratio of Sr:Li:Eu:Al of 0.9925:1.2:0.0075:3. The raw material mixture was obtained. The mass ratio of _SrNu to _SrF2 was 94:6. Since Li is easily scattered during firing, a slightly higher amount was added compared to the target composition. The raw material mixture was filled in a crucible and heat treated in a nitrogen atmosphere at 1100° C. for 3 hours at a gas pressure of 0.92 MPa in gauge pressure (1.02 MPa in absolute pressure) to obtain a powder of fired product (phosphor) 1.

(Example 1)

30 g of the fired product 1 obtained in Production Example 1 was added to 80 ml of ethanol (purity 99.5% or higher, relative dielectric constant 24 at 20°C, water content 0.03 mass%) and stirred for 3 hours. After stirring, coarse particles and fine particles were removed by classification, and solid-liquid separation and drying were performed to obtain the nitride phosphor of Example 1 having an adjusted average particle size (Dm) as shown in Table 1.

(Comparative Example 1)

The fired product 1 obtained in Production Example 1 was used as the nitride phosphor of Comparative Example 1.

(Example 2)

The nitride phosphor of Example 2 was obtained under the same conditions as in Example 1, except that pure water was added so that the water content in ethanol became 1% by mass.

(Example 3)

The nitride phosphor of Example 3 was obtained under the same conditions as in Example 1, except that pure water was added so that the water content in ethanol became 5% by mass.

(Example 4)

The nitride phosphor of Example 4 was obtained under the same conditions as in Example 1, except that pure water was added so that the water content in ethanol became 10% by mass.

(Comparative Example 2)

The nitride phosphor of Comparative Example 2 was obtained under the same conditions as in Example 1, except that pure water was added so that the water content in ethanol became 12.5% by mass.

(Comparative Example 3)

A nitride phosphor of Comparative Example 3 was obtained under the same conditions as in Example 1, except that pure water was added so that the water content in ethanol became 15.0 mass %.

(Comparative Example 4)

A nitride phosphor of Comparative Example 4 was obtained under the same conditions as in Example 1, except that pure water was added so that the water content in ethanol became 17.5% by mass.

(Comparative Example 5)

A nitride phosphor of Comparative Example 5 was obtained under the same conditions as in Example 1, except that pure water was added so that the water content in ethanol became 20% by mass.

(Comparative Example 6)

A nitride phosphor of Comparative Example 6 was obtained under the same conditions as in Example 1, except that pure water was added so that the water content in ethanol became 50% by mass.

(Example 5)

The nitride phosphor of Example 5 was obtained under the same conditions as in Example 1, except that ethanol was changed to 2-propanol (purity 99.7% or more, relative dielectric constant 18 at 20°C, water content 0.11% by mass).

(Comparative Example 7)

The nitride phosphor of Comparative Example 7 was obtained under the same conditions as in Example 1 except that ethanol was replaced with hexane (purity 96% or higher, relative dielectric constant 2 at 20°C, water content less than 0.01% by mass).

＜Evaluation＞

(X-ray diffraction pattern)

The obtained nitride phosphor was subjected to X-ray diffraction (XRD) measurements using a sample-level multifunctional X-ray diffractometer (Ultima IV, manufactured by Rigaku Corporation) using CuKα radiation. An example of the obtained XRD pattern is shown in Figure 2.

(Average particle size)

The average particle size of the obtained nitride phosphor was measured using a laser diffraction particle size distribution analyzer (MASTER SIZER 2000 manufactured by Malvern).

(Luminescence characteristics)

The luminescence characteristics of the obtained nitride phosphor were measured. The luminescence characteristics of the powder of the nitride phosphor were measured using a fluorescence spectrophotometer: QE-2000 (manufactured by Otsuka Electronics Co., Ltd.) with an excitation light wavelength of 450 nm. The relative luminescence intensity Ip (%), luminescence peak wavelength λp (nm), internal quantum efficiency (%), and external quantum efficiency (%) were calculated from the luminescence spectrum obtained. The results are shown in Table 1. It should be noted that the relative luminescence intensity Ip (%) was calculated based on the nitride phosphor of Comparative Example 1.

3 shows the emission spectra of the nitride phosphors obtained in Comparative Example 1 and Example 1. The emission spectrum in FIG3 shows the relative emission intensity with respect to the wavelength.

(Composition Analysis)

The composition ratio (molar ratio) of each element of Sr, Li, Eu, Al, and N was determined for the obtained nitride phosphor using an inductively coupled plasma emission spectrometer (manufactured by PerkinElmer) and ICP emission spectrometry. Furthermore, the contents (mass %) of O and F in the obtained nitride phosphor were measured using an oxygen/nitrogen analyzer manufactured by Horiba, Ltd. The results are shown in Table 2. It should be noted that the composition ratio (molar ratio) of each element was determined based on a composition ratio (molar ratio) of Al of 3.

(SEM photo)

Using a scanning electron microscope (SEM), SEM images of the nitride phosphors of Example 1, Example 4, and Comparative Example 6 were obtained. FIG4 is an SEM photograph of the nitride phosphor of Example 1, FIG5 is an SEM photograph of the nitride phosphor of Example 4, and FIG6 is an SEM photograph of the nitride phosphor of Comparative Example 6.

[Table 1]

[Table 2]

As shown in Table 1, the relative luminescence intensities of Examples 1-5 are all higher than those of Comparative Example 1. Furthermore, as shown in Figure 3, the luminescence spectra of Example 1 also show that the relative luminescence intensity is higher than that of Comparative Example 1. Furthermore, as shown in Table 1, the internal quantum efficiencies of Examples 1-5 are all above 80%, higher than those of Comparative Examples 1 and 5-7. Furthermore, the external quantum efficiencies of Examples 1-5 are all above 58%, higher than those of the comparative examples. Thus, Examples 1-5 exhibit improved light conversion efficiency, and by using them as phosphors in light-emitting devices, light-emitting devices capable of producing a wider light beam can be obtained. Comparative Examples 2-4, which used polar solvents with a water content exceeding 12% by mass, exhibited external quantum efficiencies of less than 55%, and also had low relative luminescence intensities. As shown in Comparative Examples 5-6, it is speculated that a water content of 20% or more in the polar solvent promotes the decomposition of the phosphor particles due to water, resulting in internal quantum efficiencies below 80% and external quantum efficiencies below 55%, resulting in reduced light conversion efficiency and relative luminescence intensity.

2 shows, from the top, XRD patterns of Comparative Example 1, Comparative Example 5, Comparative Example 6, Comparative Example 7, Example 1, Example 4, Example 5, and a reference compound (SLAN) represented by Sr ₃ Al ₂ (OH) ₁₂ , LiAl ₂ (OH) ₇ ·2H ₂ O, and SrLiAl ₃ N ₄ .

As shown in Figure 2, the compounds of Comparative Examples 1, 5-7, and Examples 1, 4, and 5 exhibit XRD patterns identical to those of SLAN, confirming that they are all compounds with a composition represented _{by SrLiAl₃N₄} . However, in Comparative Examples ₅ and ₆ , peaks for _Sr₃Al₂ (OH) _₁₂ and _LiAl₂ (OH) _₁₇ · _2H₂O are present in addition to _{SrLiAl₃N₄} , suggesting partial decomposition of the phosphor particles. As shown in Figure 2, the presence of small amounts of other compounds in addition to _{SrLiAl₃N₄} in Comparative Examples 5 and ₆ may have partially decomposed the target compound, leading to a decrease in both relative luminescence intensity and internal quantum efficiency. Comparative Example 7 uses hexane, which has a relative dielectric constant of 2 at 20°C, instead of ethanol. The relative luminescence intensity of Comparative Example 7 is not as high as in Examples 1-5, and the internal quantum efficiency is comparable to that of the other Comparative Examples, indicating no improvement in luminescence properties.

The composition ratios (molar ratios) of Sr, Eu, Li, and N shown in Table 2 are values calculated based on the composition ratio (molar ratio) of Al being 3. It should be noted that the O (oxygen) element and the F (fluorine) element are expressed in mass ratios (mass %). The oxygen (O) element in Examples 1 to 5 increased compared to that in Comparative Example 1, reaching 2 to 4 mass %. It can be considered that by dispersing the fired particles in a polar solvent having a relative dielectric constant of 10 or more and 70 or less at 20°C, the specific surface area of the particles in contact with the polar solvent is increased, and the surface of the particles is more strongly affected by the polar solvent, thereby increasing the content of oxygen in the phosphor particles. In addition, the composition ratio (molar ratio) of Eu in Examples 1 to 5 did not change substantially relative to the amount of feed, and the composition ratios (molar ratios) of Sr and Li changed slightly relative to the amount of feed. While Li is thought to decrease significantly relative to the feed amount during the heat treatment stage, the Li composition ratio (molar ratio) in the phosphor shows little change during the solvent treatment using the polar solvent described above. In Comparative Examples 2-6, since the fired particles were dispersed in a polar solvent with a high water content, the X-ray diffraction patterns (XRD) shown above indicate partial decomposition of the nitride phosphor particles. The fluorine (F) contained in the fired particles reacted with the excess water in the polar solvent, removing the fluorine. Consequently, the fluorine (F) content was reduced compared to Comparative Example 1.

No obvious difference can be confirmed in appearance between the SEM photograph of the nitride phosphor of Example 1 shown in FIG4 and the SEM photograph of the nitride phosphor of Example 4 shown in FIG5 . On the other hand, the SEM photograph of the nitride phosphor of Comparative Example 6 shown in FIG6 shows that the surface of the nitride phosphor is rough. Compared with the SEM photographs of FIG4 and FIG5 and the SEM photograph of FIG6 , the surfaces of the nitride phosphor of Example 1 and the nitride phosphor of Example 4 are relatively smooth, but as for the nitride phosphor of Comparative Example 6 in FIG6 , it can be inferred that the surface has become rough due to the partial decomposition of the nitride phosphor.

The nitride phosphor of this embodiment has excellent light emission intensity, and therefore, by using this nitride phosphor, a light emitting device with a large light beam can be provided.

Industrial Applicability

The light-emitting device using the nitride phosphor disclosed herein can be suitably used as a light source for illumination, etc. In particular, it can be suitably used as a light source for illumination having extremely excellent luminous properties using a light-emitting diode as an excitation light source, an LED display, a backlight for liquid crystal display, an annunciator, an illuminated switch, various sensors, and various indicators, etc.

Claims (18)

1. A method for manufacturing a nitride phosphor, comprising: The process of preparing a calcined article having the composition shown in formula (I) and mixing the calcined article with a polar solvent. The polar solvent is an alcohol and/or ketone containing more than 0.01% by mass and less than 12% by mass of water, Ma v M b w M c x M d y N z (I) In formula (I), Ma is at least one element selected from Sr, Ca, Ba and Mg. Mb is selected from at least one element chosen from Li, Na, and K. Mc is at least one element selected from Eu, Mn, Tb, and Ce. Md is at least one element selected from Al, B, Ga and In. v, w, x, y, and z are numbers that satisfy 0.8≤v≤1.1, 0.8≤w≤1.1, 0.001＜x≤0.1, 2.0≤y≤4.0, and 3.0≤z≤5.0, respectively. 2. The method for manufacturing a nitride phosphor according to claim 1, wherein the water content in the polar solvent is 0.1% by mass or more and 10% by mass or less. 3. The method for manufacturing a nitride phosphor according to claim 1, wherein the polar solvent is a solvent with a relative permittivity of 10 or more and 35 or less at 20°C. 4. The method for manufacturing a nitride phosphor according to claim 1, wherein the polar solvent is a lower alcohol and/or ketone of a straight-chain or branched alkyl group having 1 to 4 carbon atoms. 5. The method for manufacturing a nitride phosphor according to claim 1, wherein the polar solvent is selected from at least one of methanol, ethanol, 1-propanol, 2-propanol and acetone. 6. The method for manufacturing a nitride phosphor according to claim 1, wherein, after the step, the method includes a step of classifying the calcined material to obtain a nitride phosphor with an average particle size of 4.0 μm or more. 7. The method for manufacturing a nitride phosphor according to claim 1, wherein, in formula (I), Ma contains at least one of Sr and Ca. Mb contains Li, M c  is Eu. M d is Al. 8. The method for manufacturing a nitride phosphor according to claim 1, wherein the oxygen content in the obtained nitride phosphor is 2% by mass or more and 4% by mass or less. 9. A nitride phosphor comprising a calcined material having the composition shown in formula (I), wherein at least a portion of the calcined material particles having hydroxides or oxides on or near the surface, and wherein the oxygen content is 2% by mass or more and 4% by mass or less. M a v M b w M c x M d y N z (I) In formula (I), Ma is at least one element selected from Sr, Ca, Ba and Mg. Mb is at least one element selected from Li, Na, and K. Mc is at least one element selected from Eu, Mn, Tb, and Ce. Md is at least one element selected from Al, B, Ga and In. v, w, x, y, and z are numbers that satisfy 0.8≤v≤1.1, 0.8≤w≤1.1, 0.001＜x≤0.1, 2.0≤y≤4.0, and 3.0≤z≤5.0, respectively. 10. The nitride phosphor according to claim 9, wherein the fluorine content is 0.1% by mass or more and 1% by mass or less. 11. The nitride phosphor according to claim 9, wherein the internal quantum efficiency is 80% or higher. 12. The nitride phosphor according to claim 9, wherein, in formula (I), Ma contains at least one of Sr and Ca. Mb contains Li, M c  is Eu. M d is Al. 13. The nitride phosphor according to claim 9, wherein in the formula (I), x, y and z are numbers satisfying 0.001 < x ≤ 0.02, 2.0 ≤ y ≤ 3.5, and 3.0 ≤ z ≤ 4.0, respectively. 14. The nitride phosphor according to claim 9, wherein the fluorescence excited by light in the wavelength range of 400 nm to 570 nm has an emission peak wavelength in the wavelength range of 630 nm to 670 nm, and the external quantum efficiency exceeds 55%. 15. The nitride phosphor according to claim 9, wherein the average particle size of the nitride phosphor is 4.0 μm or more and 20 μm or less. 16. A light-emitting device comprising: The nitride phosphor according to any one of claims 9 to 12, and Excite the light source. 17. The light-emitting device according to claim 16, further comprising a second phosphor with a emission peak wavelength different from that of the nitride phosphor, the second phosphor comprising at least one phosphor having a composition selected from the following formulas: Si 6-p Al p O p N 8-p :Eu, 0＜p≤4.2 (Ca,Sr) 8 MgSi 4 O 16 (Cl,F,Br) 2 :Eu (Ba,Sr,Ca) Ga₂S₄ : Eu (Ba,Sr)MgAl 10 O 17 :Mn (Sr,Ca) AlSiN3 :Eu and K 2 (Si,Ge,Ti)F 6 :Mn. 18. The light-emitting device according to claim 16, wherein the excitation light source is a light-emitting element that emits light in a wavelength range of 400 nm or more and 570 nm or less.